In production processes for manufacturing mechanical parts or products, it is often required that XYZ coordinates on a moving or vibrating object be detected at a high speed, for measuring the dimensions of the object or for inspecting it. Especially, where the object to be investigated has a three-dimensional contour, there is strong demand for quick detection of the XYZ coordinates of numerous points on the surface of the object under investigation to efficiently and precisely measure the three-dimensional profile of the object, for grasping the geometrical features of the object. One known measuring means consists in projecting pulses of slit light onto the surface of an object and arithmetically processing only the vicinities of the two-valued slit light image to quickly detect the profile of the moving object (Japanese Patent Laid-Open No. 78109/1989).
In this known measuring means, the central position of the slit line is transformed into a thin line after the central position is converted into two values. Therefore, the ability to resolve the central position of the slit line is 0.5 picture element and thus the accuracy with which the profile is detected is poor. Also, a special camera controller and a special arithmetic control portion are necessary to read parts of TV camera signals. Hence, the system is expensive. In this way, some problems must be solved for putting the system into practical use.
The present inventor and others have devised an apparatus which detects XYZ coordinates on a real-time basis by the optical triangulation, using a slit light source and a TV camera. Each time the TV camera takes a horizontal scan, the center of gravity of the slit line is detected, and then the XYZ coordinates are detected on a real-time basis by referring to a table of data.
However, this apparatus is unable to detect XYZ coordinates appropriately. In particular, slit light is projected continuously, and the reflected light is imaged by the TV camera for 1/30 second. If the object under investigation moves during this time interval of 1/30 second, then the image is blurred.
Where disturbing light having a wide range of wavelengths such as sunlight exists in a factory or the like, a sufficiently high signal-to-noise ratio (referred to as s/n hereinafter) will not be obtained using only a band-pass filter which passes only the wavelength of the slit light source.